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From 6868dba87e2765042ac376a4a8427b9b981cd410 Mon Sep 17 00:00:00 2001
From: Phil Elwell <phil@raspberrypi.com>
Date: Tue, 16 Jan 2024 16:03:14 +0000
Subject: [PATCH 1258/1295] i2c: designware: Support non-standard bus speeds
Add support for non-standard bus speeds by treating them as detuned
versions of the slowest standard speed not less than the requested
speed.
Signed-off-by: Phil Elwell <phil@raspberrypi.com>
---
drivers/i2c/busses/i2c-designware-common.c | 27 ++++++++++++++++++++++
drivers/i2c/busses/i2c-designware-core.h | 1 +
drivers/i2c/busses/i2c-designware-master.c | 2 +-
3 files changed, 29 insertions(+), 1 deletion(-)
--- a/drivers/i2c/busses/i2c-designware-common.c
+++ b/drivers/i2c/busses/i2c-designware-common.c
@@ -318,6 +318,9 @@ void i2c_dw_adjust_bus_speed(struct dw_i
{
u32 acpi_speed = i2c_dw_acpi_round_bus_speed(dev->dev);
struct i2c_timings *t = &dev->timings;
+ u32 wanted_speed;
+ u32 legal_speed = 0;
+ int i;
/*
* Find bus speed from the "clock-frequency" device property, ACPI
@@ -329,6 +332,30 @@ void i2c_dw_adjust_bus_speed(struct dw_i
t->bus_freq_hz = max(t->bus_freq_hz, acpi_speed);
else
t->bus_freq_hz = I2C_MAX_FAST_MODE_FREQ;
+
+ wanted_speed = t->bus_freq_hz;
+
+ /* For unsupported speeds, scale down the lowest speed which is faster. */
+ for (i = 0; i < ARRAY_SIZE(supported_speeds); i++) {
+ /* supported speeds is in decreasing order */
+ if (wanted_speed == supported_speeds[i]) {
+ legal_speed = 0;
+ break;
+ }
+ if (wanted_speed > supported_speeds[i])
+ break;
+
+ legal_speed = supported_speeds[i];
+ }
+
+ if (legal_speed) {
+ /*
+ * Pretend this was the requested speed, but preserve the preferred
+ * speed so the clock counts can be scaled.
+ */
+ t->bus_freq_hz = legal_speed;
+ dev->wanted_bus_speed = wanted_speed;
+ }
}
EXPORT_SYMBOL_GPL(i2c_dw_adjust_bus_speed);
--- a/drivers/i2c/busses/i2c-designware-core.h
+++ b/drivers/i2c/busses/i2c-designware-core.h
@@ -287,6 +287,7 @@ struct dw_i2c_dev {
u16 fp_lcnt;
u16 hs_hcnt;
u16 hs_lcnt;
+ u32 wanted_bus_speed;
int (*acquire_lock)(void);
void (*release_lock)(void);
int semaphore_idx;
--- a/drivers/i2c/busses/i2c-designware-master.c
+++ b/drivers/i2c/busses/i2c-designware-master.c
@@ -41,7 +41,7 @@ static void i2c_dw_configure_fifo_master
static u16 clock_calc(struct dw_i2c_dev *dev, bool want_high)
{
struct i2c_timings *t = &dev->timings;
- u32 wanted_speed = t->bus_freq_hz;
+ u32 wanted_speed = dev->wanted_bus_speed ?: t->bus_freq_hz;
u32 clk_khz = i2c_dw_clk_rate(dev);
u32 extra_ns = want_high ? t->scl_fall_ns : t->scl_rise_ns;
u32 extra_cycles = (u32)div_u64((u64)clk_khz * extra_ns, 1000000);
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